1. Field of the Invention
Embodiments in accordance with the present invention relate to methods and systems for sensor data reporting with high positional accuracy and low power consumption.
2. Description of Related Art
Indoor Real-Time Location (RTL) Systems (RTLS) are popular in the healthcare industry for a variety of applications ranging from asset tracking through patient and staff tracking, environmental or patient sensing (e.g., temperature), hygiene compliance, elopement (i.e., a patient leaving a facility without authorization), theft prevention, and so forth.
Conventional RTL systems typically use radio frequency (RF) transmission to determine location. The RF-based methods may be augmented with infrared (IR) transmission as a localization method in order to improve accuracy to support room and sub-room level accuracies. An IR receiver typically is incorporated into a portable device (i.e., a tag) and IR transmitters are incorporated into base stations that are scattered in rooms and corridors within the enclosure. Typically, each the IR base stations transmits an identification (ID) to the portable devices, and the location of the portable devices is determined by their vicinity to a base station.
The basic advantages of synchronization of IR based systems are described in U.S. Pat. No. 8,139,945 (“the '945 Patent”), which is hereby incorporated by reference in its entirety. Timing synchronization information is transmitted using a plurality of stationary IR base stations and a plurality of portable devices. Each IR base station is configured to receive the timing synchronization information and to transmit a corresponding IR location code in a time period based on the received timing synchronization information.
In the '945 Patent, each portable device is configured: 1) to receive the timing synchronization information; 2) to detect the IR location codes from the IR base stations; and 3) to transmit an output signal including a portable device ID representative of the portable device and the detected IR location code. Each portable device is synchronized to detect the IR location code in the time period based on the received timing synchronization information. The '945 Patent enables coexistence of multiple IR transmitters at the same physical space, the construction of virtual walls, as well as facilitating high tag update rate with extremely low power consumption for tags.
However, the '945 Patent assumes that each infrared node will have its own unique infrared ID. The assumption does not apply to a configuration involving distributed IR transmissions. In such a distributed IR emitting system, all IR emitters transmit the same infrared ID at the same time. Conventionally, the only way to achieve transmitting the same infrared ID at the same time has been by use of wired connections among the independent emitters in order to allow the co-emissions of the same infrared ID from all the emitters.
Wired connections pose problems during installation and are more difficult to expand, compared to wireless connections. However, over the air super-synchronization has not been used because sufficient synchronization accuracies with low enough power consumption to support battery operated IR base-stations had not been possible or available because the timing accuracy needs to be much better than the high modulation rates (typically 30-40 kHz) of the IR signals.
Therefore, a need exists to provide a low power method to allow co-emission of the IR signals by multiple physically independent IR emitters, using the same ID from all the emitters.